The Bethesda Blog has word that the Windows and PlayStation 3 editions of the Dragonborn DLC for The Elder Scrolls V: Skyrim will be released next month. The PC edition is expected on February 5th and the PS3 edition does not have an exact date, but they say all three DLC packs should be out for Sony's system by the end of February.

I think he just grabbed the first google result. The steam source on those stats is only the concurrent users, I would be hesitant to say they accurately include digital figures in the platform totals for all three platforms. There isn't really a breakdown of DLC compared to actual unit sales either. A number of the stats seem to come directly from other articles and press releases as well, I would be interested in seeing if they confirmed them from Zenimax directly or not because I can't find any other references to platform sales breakdowns by Bethesda or Zenimax. I am not inclined to trust those figures as presented, the PC figures could easily be more or less. I do find it difficult to believe the PS3 version, which was notoriously buggy and had terrible press, outsold the PC with steam sales figured in.

The construction set tools is what they use in house, they do some work polishing them up for public consumption but it extends the game and sells more copies in the long run so it's not exactly a work of charity.